Arizona is a state riddled with anti-government white militias, radio stations pumping out racist hate speech and politicians who wave guns as they denounce the oppressive rule of Washington. But Arizona's attorney general apparently believes the real threat to the stability of the US government is being fomented in a handful of high schools in a liberal corner of the desert state.

Tom Horne has declared classes in Mexican-American history and social studies in the city of Tucson illegal on the grounds that they are "propagandising and brainwashing" students into overthrowing the constitutional government and hating white people.

Horne has ordered schools to scrap the ethnic studies programmes under a law he wrote in his previous role as Arizona's education superintendent. He has not banned similar classes dealing with black or Native American history on the grounds that no one has complained about them.

Critics, including teachers of the classes he wants to scrap, accuse Horne of political opportunism by exploiting growing hostility to people of Hispanic origin in a state that recently passed controversial anti-immigrant legislation.

José Gonzalez, who lectures at a Tucson high school, is one of 11 teachers suing to prevent that ban from being enforced.

"If you were to look at the legacy of Tom Horne and his past eight years as the superintendent of instruction in Arizona, you will see that he has targeted Mexican-American people. He did away with bilingual education. He was very proud of that," said Gonzales. "He's a politician and, quite frankly, a very successful politician so he's pandering to these xenophobic sentiments here in Arizona and that's helping him get elected."

Horne began pushing to abolish Mexican-American studies after an incident in 2007 when a prominent trade unionist, Dolores Huerta, told high school students in Tucson that Republicans hate Latinos.

Horne, a Republican, sent an aide to the school to counter the message, only to have him met by a group of students who turned their backs and raised a fist.

Infuriated, Horne blamed the teachers and wrote a law barring Arizona schools from holding classes that breached any of four prohibitions: promoting the overthrow of the government, creating resentment toward a race or class of people, focusing on students of one ethnic group or promoting ethnic solidarity.

Teachers of the offending classes acknowledge that they deal with sensitive issues, such as the past and continuing discrimination against Hispanic people in the US. They also teach the role played by figures such as César Chávez, the Mexican-American civil rights activist and trade union leader who was instrumental in improving the lot of agricultural workers, many of whom were immigrants.

Among other things, state officials have objected to classes portraying Benjamin Franklin as a racist for owning slaves and for promoting a climate of "victimisation" by teaching that white people have been more privileged in the US.

The classes involve Latino literature, although Shakespeare is on the curriculum too, as well as books such as Rodolfo Acuña's Occupied America: A History of Chicanos, which Horne has described as fostering "ethnic chauvinism" and promoting separatism.

The book, which describes Mexican- Americans as "captives of a system that renders them second-class citizens", is in its seventh edition and used at universities across the US.

The teachers say that these books are the basis for robust discussion about the past and present, which inevitably touches on race in the US – particularly in a state where about 30% of Arizona's 6.5m people are of Hispanic descent and businesses once carried signs saying: "No Mexicans or dogs allowed."

"American history is supposed to teach the history of the United States and the United States is made up of immigrants," said Gonzales. "Everyone is an immigrant here with the exception of the indigenous people, so they all have their story. The narrative that's given is traditional so Mexican-Americans' contribution to this country have been omitted and their experience has not always been a good one. We should at least be able to talk about it."

Critics said that Horne's law could mean an end to teaching about slavery because of the resentment it might cause among black students toward whites. Despite this the Arizona legislature passed the legislation last year. It was put on the statute books at the beginning of this month, just as Horne took up his new job.

Within days, he told the schools that their Mexican-American studies classes breached all four criteria, and ordered them shut down. The classes continue while the issue is resolved in the courts.

Horne has been backed by some Tucson teachers such as John Ward, who is of Hispanic origin and said the classes indoctrinate "students, based primarily on ethnic divisions, in the belief that there is a war against Latino culture perpetrated by a white, racist, capitalist system".

The Tucson school board turned down Horne's request for every Mexican-American studies class to be videotaped. But teachers say the political attacks have forced them to watch what they say in class.

"There is a chilling effect," said Lorenzo Lopez. "There's a lot more pause in what we say. Because of the unprecedented scrutiny we are a lot more cautious how we raise issues, how we discuss them. It's really hampered the dialogue that takes place."